Spinal distraction system

ABSTRACT

A spinal distraction system including a bearing connector fastened to a fixated rod and a sliding rod, wherein the sliding rod includes a spring and a stop ring is disclosed. A method of distracting vertebrae is also disclosed.

FIELD OF THE INVENTION

The invention relates generally to a spinal distraction system includinga first set of rods, a second set of rods, a fastener, a connector, anda spring. The spinal distraction system can be active and/or dynamic innature.

BACKGROUND OF THE INVENTION

Spinal deformation during skeletal growth is a disorder with potentialdevastating consequences. Surgical treatment options are bothersomebecause correction and fusion of the deformation is incompatible withmaintaining growth of the spine. Growing systems have also been usedlike growing rods, VEPTR, and recently magnetically controlled growingrods. However, these growing systems may require repeat operations orrepeat elongations at certain intervals. These intervals are not similarto normal gradual growth of the spine, allow the spine to stiffenbetween lengthenings, lead to unphysiological strains on the tissues atthe moment of lengthening, and can be a burden on the patient. In caseswhere surgical releases of the spine are to be performed, such ascongenital deformations, the spine can re-fuse soon after operativerelease and static fixation with any current growth system and furthergrowth may be impossible even with repetitive distractions.

SUMMARY OF THE INVENTION

In an aspect, there is disclosed a spinal distraction system comprisinga bearing connector fastened to a fixated rod and a sliding rod, whereinthe sliding rod includes a spring and a stop ring.

In another aspect, there is disclosed a method for distractingvertebrae, including inserting a first set of a plurality of fastenersinto adjacent vertebrae in a first region; inserting a fixation rod intothe first set of the plurality of fasteners; inserting a caudad end ofthe fixation rod into a bearing connector; inserting a second set of aplurality of fasteners into adjacent vertebrae in a second region;loading a stop ring and a spring onto the sliding rod; sliding thecephalad end of the sliding rod into the bearing connector so that thespring is disposed between the bearing connector and the stop ring; andinserting the caudad end of the sliding rod into the second set of aplurality of fasteners.

Additional objects and advantages of the invention will be set forth inpart in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention will be realized and attained bymeans of the elements and combinations particularly pointed out in theappended claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present disclosure are described herein belowwith reference to the drawings, wherein:

FIG. 1A is an isometric view of an example spinal distraction systemaccording to an aspect of the present invention;

FIG. 1B is a close-up of FIG. 1A;

FIG. 2A is an example bearing connector according to an aspect of thepresent invention;

FIG. 2B is an exploded view of FIG. 2A;

FIG. 2C is a cross-section of FIG. 2D;

FIG. 2D is a top view of FIG. 2A;

FIG. 2E is a side view of FIG. 2A;

FIG. 3A is an isometric view of an example housing of the bearingconnector according to an aspect of the invention;

FIG. 3B is an alternative isometric view of FIG. 3A;

FIG. 4A is an isometric view of an example bearing of the bearingconnector according to an aspect of the invention;

FIG. 4B is a top view of FIG. 4A;

FIG. 4C is a side view of FIG. 4A;

FIG. 5 is a view of an example fixated rod according to an aspect of theinvention;

FIG. 6 is a view of an example fixated rod and fasteners according to anaspect of the invention;

FIG. 7 is a view of an example sliding rod with a loaded spring and astop ring according to an aspect of the invention;

FIG. 8 is a view of the sliding rod inserted into the bearing connectoraccording to an aspect of the invention; and

FIG. 9 is a view of a compressor compressing the spring and stop ringaccording to an aspect of the invention.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Various embodiments will now be described in detail with reference tothe drawings, wherein like reference numerals identify similar oridentical elements. In the drawings and in the description that follows,the term “proximal”, as is traditional, will refer to the end of thedevice which is closest to the operator while the term “distal” willrefer to the end of the device which is furthest from the operator. Theterm “cephalad” is used in this application to indicate a directiontoward a patient's head, whereas the term “caudad” indicates a directiontoward the patient's feet. Further still, for the purposes of thisapplication, the term “medial” indicates a direction toward the middleof the body of the patient, whilst the term “lateral” indicates adirection toward a side of the body of the patient (i.e. away from themiddle of the body of the patient) The term “posterior” indicates adirection toward the patient's back, and the term “anterior” indicates adirection toward the patient's front. Additionally, in the drawings andin the description that follows, terms such as front, rear, upper,lower, top, bottom and the similar directional terms are used simply forconvenience of description and are not intended to limit the disclosureattached hereto.

As shown in FIGS. 1A and 1B, the present disclosure is directed to aspinal distraction system 10 including a bearing connector 20 fastenedto fixated rod 14 and a sliding rod 16, wherein the sliding rod 16includes a spring 22 and a stop ring 18. The spinal distraction system10 can provide continuous distraction to vertebrae. The magnitude of thedistraction force can be adjusted intraoperatively by a surgeon basedupon tactile feedback or a pre-tension/length table. Additionally, thespinal distraction system 10 can be used in combination with existingposterior spinal fusion systems.

FIGS. 2A-2E illustrate the bearing connector 20. The bearing connector20 includes a set screw 24, a bearing 30, and a housing 21. The housing21 can include a top surface 36, a bottom surface 38, and side surfaces46, 47, as shown in FIGS. 3A-3B. The top surface 36 and the bottomsurface 38 define a hollow 40 that can be configured and dimensioned toreceive a rod, such as the fixated rod 14, as shown in FIGS. 1A-1B. Therod can be side-loaded into the hollow 40 and then secured in place byrotation of the set screw 24. Alternatively, the top surface 36 can havea defined hollow (not shown) that can be configured and dimensioned toreceive the fixated rod 14. In this manner, the rod can be top-loadedinto the hollow and then secured in place by rotation of a set screwthat would be located on a side surface 46, 47. In an alternativeembodiment, the bottom surface 38 can define a hollow that can beconfigured and dimensioned to receive the fixated rod 14. In thismanner, the rod can be bottom-loaded into the hollow and then secured inplace by rotation of a set screw that would be located on a side surface46, 47.

As shown in FIGS. 2B, 3A, and 3B the housing 21 of the bearing connector20 can include a first bore 42 that can extend from a first beveled sidesurface 49 to a second beveled side surface 50. In an aspect, the spring22 can abut either of the first beveled side surface 49 or secondbeveled side surface 50. The first bore 42 can be configured anddimensioned to receive the bearing 30. In particular, the first bore 42can include a concave inner surface 44 that mates with a convex outersurface 34 of the bearing 30. In this manner, the bearing 30 can freelyrotate in a polyaxial manner within the housing 21 of the bearingconnector 20. As shown in FIGS. 4A-4C, the bearing 30 can include asecond bore 32 configured and dimensioned to receive the sliding rod 16.

The bearing connector 20 aligns passively with a rod, such as thesliding rod 16 with minimal friction. In this manner, there can be areduction in growth resistance and metal debris. Metal debris can beassociated with foreign body reactions, granuloma's and even low gradeinfections. The bearing connector 20 can also allow some sagittalmotion, which can be enlarged by adding an extra rotational axis betweenthe bearing connector 20 and the fastener 12. The ability of the spinaldistraction system 10 to allow some sagittal motion also enables thespinal distraction system 10 to absorb energy which can prevent thespinal distraction system 10 from fatigue failure.

The spinal distraction system 10 can include, instead of the bearingconnector 20, any connector that would provide for parallel connectionof the fixated rod 14 and the sliding rod 16. For example, the connectorcould be two bores adjacent to one another with two set screws to securethe rods within, where one set screw is left out to allow sliding.

As shown in FIG. 7, the sliding rod 16 can be loaded with a spring 22and a stop ring 18. In an aspect, the spinal distraction system 10 caninclude a stop ring 18. The stop ring 18 can include a bore (not shown)and a set screw. The sliding rod 16 can be inserted through the bore ofthe stop ring 18. The stop ring 18 can be positioned anywhere along thelength of the sliding rod 16. At a predetermined position, the set screwof the stop ring 18 can be tightened to secure the stop ring 18 alongthe sliding rod 16 at the predetermined position, such as aftercompression of the spring 22.

The spring 22 also contains a bore (not shown) that can be configuredand dimensioned to receive a rod, such as the sliding rod 16. The spring22 should be loaded so that one end of the spring 22 abuts the stop ring18, as shown in FIG. 7. The spring 22 can be made of any biocompatiblematerial including metals and polymers, such as titanium. The spring 22can be any gauge so long as the spring 22 is able to distract thevertebrae over a period of time. In an aspect, the distraction forceprovided by the spring 22 should be about 50 to about 250 Newtons, forexample from about 55 to about 225 Newtons, and as a further examplefrom about 60 to about 200 Newtons. This distraction force can beprovided by a spring 22 with a compressed length from about 3 to about 5centimeters, such as about 3.2 to about 4.9 centimeters, and as afurther example from about 4.3 to about 4.8 centimeters. The spring 22can have an uncompressed (relaxed) length of about 3 to about 15centimeters, for example from about 8 to about 13.8 centimeters, and asa further example from about 8.4 to about 9.6 centimeters. It should benoted that the spring 22 can be compressed during the initialinstallation of the spinal distraction system 10, but can also becompressed at any time thereafter depending upon the spinal growth. Itis envisioned that any compression of the spring 22 after the initialcompression would not be needed until several years later and wouldinvolve a minimal surgical procedure.

In an aspect, the spinal distraction system 10 can include one spring,two springs, three springs, etc. The number of springs 22 can bedetermined based upon the uncompressed length of the spring 22 as wellas the optimal distracted length of the vertebrae. For example, thespinal distraction system 10 can include one spring 22 having anuncompressed length of 6 centimeters and a compressed length of 3centimeters because the optimal distracted length of the involvedvertebrae is 3 centimeters. Alternatively, the spinal distraction system10 can include two springs 22 in series, each having an uncompressedlength of 3 centimeters because the optimal distracted length of theinvolved vertebrae is 6 centimeters.

In an aspect, the spring 22 can be a mini-spring (not shown), forexample, having an uncompressed length ranging from about 0.5 cm toabout 3 cm, such as from about 0.75 cm to about 2.75 cm, including anuncompressed length from about 1.0 cm to about 2.5 cm. The mini-springcan be loaded onto a rod, such as the sliding rod 16 of the spinaldistraction system 10. The mini-spring 22 can also be used withconventional growing rods and/or magnetically controlled rods, incombination with a sliding connector, leading to a more dynamic spinalfixation. Such a spinal distraction system including at least onemini-spring 22 can be less prone to fatigue failure and spontaneousfusion.

In an aspect, the spinal distraction system 10 can include a sleeve orsheath (not shown) that can extend over at least a portion of a lengthof the spring 22 to minimize tissue ingrowth. In an aspect, the sleeveextends over 50% of the length of the spring 22, for example over 75% ofthe length, and as a further example over 100% of the length of thespring 22. The sleeve or sheath could be a flexible tube, cloth, orwoven material, for example. In another aspect, the spring 22 can becoated with a biocompatible material, such as a polymer, that prohibitsand/or minimizes tissue growth. In another aspect, the spring 22 can beintegrated in cellular foam with closed cells. The combination of thesleeve/sheath and spring 22 should not allow for any dead space whichcould provide an area susceptible to infection.

The spinal distraction system 10 can be used in multiples. For example,a spinal distraction system 10 can be used singly or can be used as apair.

The spinal distraction system 10 can be used in a method for distractingvertebrae. The method includes forming a hole in a vertebra. In anaspect, two holes can be formed in a vertebra. In another aspect, twoholes can also be formed into an adjacent vertebra. The vertebrae caneach have two holes formed therein and can be in a first region 52, suchas a cephalad region of a spinal column. Similarly, two holes can beformed in a vertebra and two holes can also be formed into an adjacentvertebra in a second region 54, such as a caudad region of a spinalcolumn. The method can further include inserting into the formed holes afirst set of a plurality of fasteners 12 into adjacent vertebrae in thefirst region 52, as shown in FIGS. 1A, 1B, and 5. One of ordinary skillin the art can determine the location along a length of the spinalcolumn for the first region 52 relative to the second region 54.

The method can include inserting a first set of a plurality of fasteners12 into the formed holes of adjacent vertebrae in the first region 52.An insertion tool can be used. The fasteners 12 can be any mechanicalhardware, such as screws, including pedicle screws. In an aspect, eachfastener of the plurality of fasteners 12 can include a head having atrough 56 configured and dimensioned to receive a rod, such as a fixatedrod 14 and/or a sliding rod 16. In an aspect, the method can includeinserting a fixated rod 14 into the first set of the plurality offasteners 12. A caudad end of the fixated rod 14 can be inserted into abearing connector 20, as shown in FIG. 5, such as the hollow 40 of thebearing connector 20. In another aspect, the bearing connector 20 can beinserted onto the caudad end of the fixated rod 14, and then the fixatedrod 14 can be inserted into the troughs 56 of the first set of theplurality of fasteners 12. In an aspect, the method can further includelocking the fixated rod 14 into the first plurality of fasteners 12.

The method can include inserting a second set of a plurality offasteners 12 into adjacent vertebrae in a second region 54, as shown inFIG. 6. One of ordinary skill in the art will realize that this step canalso be performed at the same time as inserting the first set of aplurality of fasteners 12 into adjacent vertebrae in the first region52. In particular, the first and second set of the plurality offasteners 12 can be inserted into the insertion holes in any order,i.e., first region 52 and then second region 54, or second region 54 andthen first region 52. Additionally, both of the first and second set ofthe plurality of fasteners 12 can be inserted before the fixated rod 14is inserted into the first region 52. In an aspect, the method canfurther include locking the sliding rod 16 into the second set ofplurality of fasteners 12.

The method can include loading a stop ring 18 and a spring 22 onto asliding rod 16, as shown in FIG. 7. Once the stop ring 18 is positionedat a predetermined location along a length of the sliding rod 16 a setscrew associated with the stop ring 18 can be rotated to tighten thestop ring 18. In an aspect, the set screw associated with the stop ring18 can be left loose until a later time, such as after the spring 22 arecompressed. In an aspect, the sliding rod 16 can be bent along itslength before loading of the spring 22 and the stop ring 18.

The method can include sliding an end of the sliding rod 16 into thebearing connector 20 so that the spring 22 is disposed between thebearing connector 20 and the stop ring 18, as shown in FIG. 8. Inparticular, a cephalad end of the sliding rod 16 can be inserted into abearing of the bearing connector 20. A portion of the sliding rod 16 canextend through and beyond the bearing connector 20. The spring 22 canabut a beveled side surface 49 of the bearing connector 20 at one endand the stop ring 18 on another end. In an aspect, the portion of thesliding rod 16 that extends beyond the bearing connector 20 can beparallel to the fixated rod 14. An opposite end of the sliding rod 16can extend towards and beyond the second set of the plurality offasteners 12 in the second region 54. The opposite end of the slidingrod 16 can be inserted into the second set of a plurality of fasteners12. The bearing connector 20 can provide continuous alignment with thesliding rod 16 and sagittal motion.

The method can further include compressing the spring 22, as shown inFIG. 9. An instrument 58 can be positioned so that the bearing connector20, spring 22, and stop ring 18 are between the ends of the instrument58. A force can be applied to a handle of the instrument 58 so that thestop ring 18 applies a force against the spring 22 thereby compressingthe spring 22 against the bearing connector 20. A force can be appliedto the set screw associated with the stop ring 18 locking the stop ring18 in place against the compressed spring 22.

The method can further include compressing the spring 22 a second timeafter a period of time to provide a continuous distraction of thevertebrae.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

1. A spinal distraction system comprising: a bearing connector fastenedto a fixated rod and a sliding rod, wherein the sliding rod includes aspring and a stop ring.
 2. The system of claim 1, wherein the bearingconnector includes a set screw, a bearing and a housing, wherein thehousing has a top surface and a bottom surface that define a hollow. 3.The system of claim 2, wherein the hollow is configured and dimensionedto receive the fixated rod.
 4. The system of claim 1, wherein thebearing connector includes a first bore that extends from a firstbeveled side surface to a second beveled side surface.
 5. The system ofclaim 1, wherein the first bore is configured and dimensioned to receivea bearing.
 6. The system of claim 1, wherein the first bore includes aconcave inner surface.
 7. The system of claim 5, wherein the bearingincludes a second bore configured and dimensioned to receive the slidingrod.
 8. The system of claim 1, wherein the spring abuts a beveled sidesurface of the bearing connector.
 9. The system of claim 1, furthercomprising a sleeve that extends over at least a portion of a length ofthe spring.
 10. The system of claim 1, further comprising a stop ring.11-20. (canceled)